You have it written. "Players can fight enemies or other players at a private party in an active old school combat system using weapons and magic." I propose to make the game multi-user and with a virtual reality. Imagine you are at a party, and there are a bunch of your colleagues with glasses of virtual reality. What can the party turn out into?
Not sure if this works for 2d tiled based games. However There are some great other projects that implements virtual 3d into the world, decentraland for example.
This game is 2d oriented, to get the old school simplicity and feeling.
As a gamers perspective sometimes the envirement or the visuals doesn't realy matter that much, its the gameplay that is important to get players hooked, Mario is a good example, 2d side scrolling 8bit graphics and still played.
We can do some co-op maps where 2 or more players enter and need to work thogether to get to the finnish, the possibillities are endless never the less.